1. Field of the Invention
The present invention relates to a photographing apparatus including an autofocus function.
2. Description of the Related Art
According to Japanese Patent Application Laid-Open No. 8-248510, in a complex camera including a still camera unit, a video camera unit, and a photographic lens common to the units, a control device performs a servo control based on repeated detections of the focus detection device if a movement detecting device detects that a subject is moving during still image photographing, and performs a one shot control, in which the lens drive is terminated once the lens is focused and then the focus is locked, if it is detected that the subject is not moving.
Japanese Patent Application Laid-Open No. 2003-207712 discloses an imaging apparatus that adjusts the focus of an optical device, the imaging apparatus comprising: an optical unit that receives a light beam from a subject to generate a subject image; a contrast detecting unit that detects a contrast value of the subject image; a ranging unit that calculates range information indicative of a distance from the focusing apparatus to the subject; an adjustment instruction accepting unit that accepts instruction information indicative of adjustment of the focus of the optical unit; a focus control unit that adjusts the focus of the optical unit when the adjustment instruction accepting unit accepts the instruction information; and a range information storing unit that stores a contrast value detected by the contrast detecting unit when the adjustment instruction accepting unit accepts the instruction information and range information calculated by the ranging unit.
In Japanese Patent Application Laid-Open No. 2002-258344, an arithmetic processing circuit executes, in response to a first instruction from a release SW for starting photographing, AE and AF processes based on a signal outputted from an imaging element to control the lens position, the aperture size, and the shutter speed of the imaging element and keeps an elapsed time from the acquisition of the first instruction to the acquisition of a second instruction that is instructed following the first instruction and that is from the release SW for starting photographing. In the photographing started according to the second instruction, the arithmetic processing circuit executes the AE and AF processes based on the elapsed time, and if the elapsed time is short, the arithmetic processing circuit diverts a control result of the AE and AF processes executed in the photographing started according to the first instruction without executing one or both of the AE and AF processes.
In Japanese Patent Application Laid-Open No. 2003-232984, according to a focus instructing operation, a CPU compares, before the focusing operation, current image data obtained just after the focus instructing operation with the focus lens at a last-time in-focus position detected by the focusing operation of the last time and last-time image data that is obtained during the focusing operation of the last time or just after the end of the focusing operation of the last time with the focus lens at the last-time in-focus position. The CPU then determines whether the focused state from the focusing operation of the last time is maintained. If not maintained, the CPU does not drive the focus lens in the in-focus position detection or narrows down the driving region of the focus lens.
In Japanese Patent Application Laid-Open No. 8-76169, a focus adjusting lens is set at the hyperfocal distance in advance. Once an operation for starting a photographing preparation operation is performed, a photometric device ALS is activated, and then whether an aperture value obtained from calculated photometric information is greater than a predetermined aperture value is compared. If it is greater, the photographic operation is permitted. If it is smaller, distance measuring devices AFS and AFC are activated. A control device MPU for permitting the photographic operation is installed after activating a lens driving unit LM based on calculated distance measurement information. If an aperture value obtained as a result of photometry is greater than a predetermined aperture value, a subject can be focused at the depth of field of the lens set at the hyperfocal distance. Therefore, the releasing is immediately performed without driving the lens. In other cases, the lens is driven.